Sports fields are typically designed to have suitable compaction, drainage, and water management attributes. In many regions around the world, sports fields surfaces are built with multiple layers of aggregate materials that help to improve the speed of water to drain through these layers and for suitable water retention so as not to involve significant irrigation of turf.
When using sandy type soils disposed over a relatively coarser gravel layer, a perched water table is typically formed. This practice, developed by Dr. Marvin Ferguson and the United States Golf Association, has evolved in construction specifications since the early 1960s as a method called the USGA Green construction Method. This and similar methods have been used in golf greens and sports fields. Other Methods such as the Prescription Athletic Field (“PAT”) system evolved from this practice, with golf bunker construction using drainage layers and liners that employ a coarse aggregate below the sandy soil as a technique for providing fast drainage.
A perched water table of the above-described designs may allow a surface layer to drain and may retain water between rain events or irrigation cycles so that less water is used in irrigation and turfgrass can survive in droughts. A perched water table can be used in playing surfaces in areas such as golf sand bunkers.
When golf bunker sand is wet, it is typically firmer. By retaining moisture, the bunker does not have as many undesirable buried or “fried egg lies” when a golf ball lands in the bunker. These buried lies are typically undesirable for golfers.
Very wet playing surfaces are typically undesirable and may cause various problems. For turf surfaces, prolonged existence of excessive water is not good for the turf and can accelerate disease and anaerobic conditions, which may cause quick turf decline. Water may move relatively slower when moving laterally in sand, making low areas on putting greens more difficult to manage due to having excessive water compared to relatively higher locations on the playing surfaces. This issue may also occur on sports fields that are crowned or pitched. For example, golf bunkers that are flat and sloped may be wetter in its low areas where most golf shots are hit from. If sand is too shallow, or a recent rain event or irrigation has occurred, the sand's playing surface may be less desirable. A relatively fast draining system, such as a USGA green or sports fields using a gravel layer below the playing surface soil may hold excessive moisture immediately after a rain or irrigation event due to perching of water in sand disposed over the gravel layer. In climates where evaporation is relatively slow, sand disposed in playing surface layers may not dry fast enough in its low levels. Providing suitable speed or time of drying after these rain cycles in order to achieve suitable playing surface conditions is typically a problem.
If a sandy soil sits over relatively coarse soil, a perched water table typically occurs. Such a soil that has received adequate water to fill the entire profile is at field capacity. When a perched water table exists, the soil stops draining and remains at field capacity. The amount of time in which gravity can pull the water down and achieve the desired moisture in these sports surfaces is longer in the relatively lower areas of conventional systems, which may result in playing surfaces being wetter than desired and being unsuitable for growing turf or playing sports.
Due to gravity and a lateral movement of water through sands, surface layers are typically wetter in low areas than in higher sections. The amount of time it may take for a playing surface to become drier affects suitability for playing. Conventional techniques show that removing water from the surface and subsurface drainage and proper design of drainage devices such as pipes may provide a good playing surface. This “Stormwater” design is calculatable to determine pipe sizes for collection and removal of water from a playing surface site. Subsurface water calculation is determined by the layers of a surface. A percolation rate of the top layers dictates how quickly water moves into the next layer. Gravitational pull being consistent, as long as the layer of aggregates below is larger than aggregates above, water will move downward vertically while the soil is saturated or above field capacity until the upper soil reaches field capacity. When the layer of aggregates of the upper soil is smaller than the next lowest layer, a perched water table will exist and the soil will remain at a field capacity, totally saturating the two layers. The soil will remain at field capacity and stop releasing water until additional water enters the soil from above and then it will release water based on a 1:1 ratio. Drainage devices such as pipes may release water faster. A perched water table slows the drying of the soils in the lower levels of playing surfaces because of the speed in which sand moves water laterally over these perched water tables (e.g., because the space below is void of air). Increasing the depth of sand in playing surfaces or eliminating perched water may speed drying, but are costly.
It is beneficial for playing surfaces to have relatively quick draining characteristics in its relatively low areas during heavy rain seasons or heavy irrigation cycles (e.g., in coastal areas where summer rains can occur daily). When these seasonal rains occur, systems that perch water may remain at field capacity based on the speed in which the sand layer can drain and release the water (e.g., percolation rate) to the gravel layer.
Concerns may also exist involving conventional gravel bridging with existing subgrade soils. If a subgrade is relatively fine and does not bridge with the aggregate, the fines may clog a drain pipe.
Another problem involves surface layers being irrigated with effluent water and/or using high fertility. A sports-turf sandy soil may begin to drain slower soon after construction, resulting in a surface involving additional cultivational practices such as coring and raking to assist in improving drying of the surfaces. When such soils remain excessively wet, additional issues such as turf disease, root rotting, algae, and anaerobic conditions may occur. These additional issues may compound problems by changing the way in which the soil drains. Sands, which may have drained relatively quickly initially, may become contaminated in less than a year and perform 25% or less of the original drainage percolation rates or capacity.
A further problem associated with sports fields is that drainage in relatively higher locations is typically faster than relatively lower areas due to relatively slower movement of water in a sand layer laterally toward relatively lower regions. When a perched water table occurs, the relatively lower areas of the sports field may be wetter. Another problem involving sports fields may be that some areas (e.g., golf bunkers) may not be flat and soils in this area may be unstable.
The exemplary disclosed apparatus, system, and method of the present disclosure is directed to overcoming one or more of the shortcomings set forth above and/or other deficiencies in existing technology.